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AP Chem

EquilibriumWorksheet Packet

WS#1: Equilibrium Expression and Calculations for K/KP

  1. Write the expressions for (K) and (KP).
  2. N2(g) + O2(g) ↔ 2NO(g)
  3. N2O4(g) ↔ 2NO2(g)
  4. SiH4(g) + 2Cl2(g) ↔ SiCl4(g) + 2H2(g)
  5. 2PBr3(g) + 3Cl2(g) ↔ 2PCl3(g) + 3Br2(g)
  6. P4(s) + 5O2 ↔ P4O10(s)
  7. NH4NO3(s) ↔ N2O(g) + 2H2O(g)
  8. CO2(g) + NaOH(s) ↔ NaHCO3(s)
  9. S8(s) + 8O2(g) ↔ 8SO2(g)
  10. At a given temperature, K = 1.3x10-2 for the reaction N2(g) + 3H2(g) ↔ 2NH3(g). Calculate the values of K for the following reactions at this temperature.
  11. 1/2 N2(g) + 3/2H2(g) ↔ NH3(g)
  12. 2NH3(g) ↔ N2(g) + 3H2(g)
  13. NH3(g) ↔ 1/2N2(g) + 3/2H2(g)
  14. 2N2(g) + 6H2(g) ↔ 4NH3(g)
  15. At high temperatures, elemental nitrogen and oxygen react with each other to form nitrogen monoxide: N2(g) + O2(g) ↔ 2NO(g), Suppose the system is analyzed at a particular temperature, and the equilibrium concentrations are found to be [N2] = 0.041M, [O2] = 0.0078M, and [NO] = 4.7x10-4M. Calculate the value of K for the reaction.
  16. At a particular temperature, a 3.0L flask contains 2.4mol Cl2, 1.0mol NOCl, and 4.5x10-3mol NO. Calculate K at this temperature for the following reaction: 2NOCl(g) ↔ 2NO(g) + Cl2(g).
  17. The following equilibrium pressures were observed at a certain temperature for the reaction 2NO2(g) ↔ 2NO(g) + O2(g).

PNO2 = 0.55atm, PN2 = 8.5x10-1atm, and PH2 = 3.1x10-3atm. Calculate the value of KP at this temperature.

  1. At 25oC, K = 3.7x109 for the reaction CO(g) + Cl2(g) ↔ COCl2(g) . Calculate KP at this temperature.
  2. Write expressions for K and Kp for the following reactions:
  3. P4(s) + 5O2(g) ↔ P4O10(s)
  4. NH4NO3(s) ↔ N2O(g) + 2H2O(g)
  5. CO2(g) + NaOH(s) ↔ NaHCO3(s)
  6. S8(s) + 8O2(g) ↔ 8SO2(g)
  7. Consider the following reaction at a certain temperature: 4Fe(s) + 3O2(g) ↔ 2Fe2O3(s). An equilibrium mixture contains 1.0mol Fe, 1.0x10-3mol O2, and 2.0mol Fe2O3 all in a 2.0L container. Calculate the value of K for this reaction.

WS#2: Equilibrium Calculations and Le Chatelier’s Principle

  1. The equilibrium constant, K, is 2.4x103 at a certain temperature for the reaction 2NO(g) ↔ N2(g) + O2(g). For which of the following sets of conditions is the system at equilibrium? If not at equilibrium, which way will it shift?
  2. A 1.0L flask contains 0.024mol NO, 2.0mol N2, and 2.6mol O2.
  3. A 2.0L flask contains 0.032mol NO, 0.62mol N2, and 4.0mol O2.
  4. A 3.0L flask contains 0.060mol NO, 2.4mol N2, and 1.7mol O2.
  5. At 900oC, KP = 1.04 for the reaction, CaCO3(s) ↔ CaO(s) + CO2(g). At a low temperature, dry ice (solid CO2), calcium oxide, and calcium carbonate are introduced into a 50.0L reaction chamber. The temperature is raised to 900oC, resulting in the dry ice converting to gaseous CO2. For the following mixtures, will the initial amount of calcium oxide increase, decrease, or remain the same as the system moves toward equilibrium at 900oC?
  6. 655g CaCO3, 95.0g CaO, PCO2 = 2.55atm
  7. 780g CaCO3, 1.00g CaO, PCO2 = 1.04atm
  8. 0.14g CaCO3, 5000g CaO, PCO2 = 1.04atm
  9. 715g CaCO3, 813g CaO, PCO2 = 0.211atm
  10. The equilibrium constant, K, for the reaction, H2(g) + F2(g) ↔ 2HF(g) has the value 2.1x103 at a particular temperature. When the system is analyzed at equilibrium at this temperature, the concentrations of H2(g) and F2(g) are both found to be 0.0021M. What is the concentration of HF(g) in the equilibrium system under these conditions?
  11. A 1.00L flask was filled with 2.00mol gaseous SO2 and 2.00mol gaseous NO2 and heated. After equilibrium was reached, it was found that 1.30mol gaseous NO was present. Assume that the reaction SO2(g) + NO2(g) ↔ SO3(g) + NO(g) occurs under these conditions. Calculate the value of the equilibrium constant, K, for this reaction.
  12. At a particular temperature, 12.0mol of SO3 is placed into a 3.0L rigid container, and the SO3 dissociates by the reaction 2SO3(g) ↔ 2SO2(g) + O2(g). At equilibrium, 3.0mol of SO2 is present. Calculate Kfor this reaction.
  13. At a particular temperature, K = 3.75 for the reaction SO2(g) + NO2(g) ↔ SO3(g) + NO(g). If all four gases had initial concentrations of 0.800M, calculate the equilibrium concentrations of the gases.
  14. At 2200oC, KP = 0.050 for the reaction N2(g) + O2(g) ↔ 2NO(g). What is the partial pressure of NO in equilibrium with N2 and O2 that we placed in a flask at initial pressures of 0.80 and 0.20atm, respectively?
  15. At 1100K, KP = 0.25 for the reaction 2SO2(g) + O2(g) ↔ 2SO3(g). Calculate the equilibrium partial pressures of SO2, O2, and SO3 produced from an initial mixtures in which PSO2 = PO2 = 0.50atm, and PSO3 = 0. (Hint: If you don’t have a graphing calculator, then use the method of successive aapproximations to solve, quadratic equation.)
  16. At 35oC, K = 1.6x10-5 for the reaction 2NOCl(g) ↔ 2NO(g) + Cl2(g). Calculate the concentrations of all species at equilibrium for each of the following original mixtures.
  17. 2.0mol pure NOCl in a 2.0L flask
  18. 1.0mol NOCl and 1.0mol NO in a 1.0L flask
  19. 2.0mol NOCl and 1.0mol Cl2 in a 1.0L flask
  20. At a particular temperature, K = 2.0x10-6 for the reaction 2CO2(g) ↔ 2CO(g) + O2(g). If 2.0mol CO2 is initially placed into a 5.0L vessel, calculate the equilibrium concentrations of all species.
  21. At 25oC, KP = 2.9x10-3 for the reaction NH4OCONH2(s) ↔ 2NH3(g) + CO2(g). In an experiment carried out at 25oC, a certain amount of NH4OCONH2 is placed in an evacuated rigid container and allowed to come to equilibrium. Calculate the total pressure in the container at equilibrium.
  22. Suppose the reaction system UO2(s) + 4HF(g)↔ UF4(g) + 2H2O(g) has already reached equilibrium. Predict the effect that each of the following changes has on the equilibrium position. Tell whether the equilibrium will shift to the right, left, or remain the same.
  23. Additional UO2(s) is added to the system.
  24. The reaction is performed in a glass reaction vessel; HF(g) attacks and reacts with glass.
  25. Water vapor is removed.
  26. An important reaction in the commercial production of hydrogen is CO(g) + H2O(g) ↔ H2(g) + CO2(g). How will this system at equilibrium shift in each of the five following cases?
  27. Gaseous carbon dioxide is removed.
  28. Water vapor is added.
  29. The pressure is increased by adding helium gas.
  30. The temperature is increased (the reaction is exothermic).
  31. The pressure is increased by decreasing the volume of the reaction container.
  32. In which direction will the position of the equilibrium 2HI(g) ↔ H2(g) + I2(g) be shifted for each of the following changes?
  33. H2(g) is added.
  34. I2(g) is removed.
  35. HI(g) is removed
  36. The reaction to prepare methanol from hydrogen and carbon monoxide, CO(g) +2H2(g) ↔ CH3OH(g), is exothermic. If you wanted to use this reaction for producing methanol commercially, would high or low temperatures favor a maximum yield?

WS#3: Combined Problems

  1. Calculate the value for the equilibrium constant for the reaction O2(g) + O(g) ↔ O3(g) given

hν

NO2(g) ↔ NO(g) + O(g) K = 6.8x10-49

O3(g) + NO(g) ↔ NO2(g) + O2(g) K = 5.8x10-34

Hint: When reactions are added together, the equilibrium constants are multiplied.

  1. An initial mixture of nitrogen has and hydrogen gas is reacted in a rigid container at a certain temperature by the reaction 3H2(g) + N2(g) ↔ 2NH3(g). At equilibrium, the concentrations are [H2] = 5.0M, [N2] = 8.0M, and [NH3] = 4.0M. What were the concentrations of nitrogen gas and hydrogen gas that were reached initially?
  2. For the reaction PCl5(g) ↔ PCl3(g) + Cl2(g) at 6oo.K, the equilibrium constant, KP, is 11.5. Suppose that 2.450g PCl5 is placed in an evacuated 500.mL bulb, which is then heated to 600.K.
  3. What would be the pressure of PCl5 if it did not dissociate?
  4. What is the partial pressure of PCl5 at equilibrium?
  5. What sit e total pressure in the bulb at equilibrium?
  6. What is the degree of dissociation of PCl5 at equilibrium?
  7. For the following reaction at a certain temperature H2(g) + F2(g) ↔ 2HF(g) it is found that the equilibrium concentrations in a 5.00L rigid are [H2] = 0.0500M, [F2] = 0.0100M, and [HF] = 0.400M. If 0.200mol of F2 is added to this equilibrium mixture, calculate the concentrations of all gases once equilibrium is reestablished.
  8. Chromium (VI) forms two different oxyanions, the orange dichromate ion, Cr2O72-, and the yellow chromate ion, CrO42-. The equilibrium reaction between the two ions is Cr2O72-(aq) + H2O(l) ↔ 2CrO42-(aq) + 2H+(aq). Explain why orange dichromate solutions turn yellow when sodium hydroxide is added.

Extra Credit Problems (2.5pts per question. No teacher help. Must be correct to receive points.)

  1. At 35oC, K = 1.6x10-5 for the reaction 2NOCl(g) ↔ 2NO(g) + Cl2(g). if 2.0mol NO and 1.0molCl2 are placed into a 1.0L flask, calculate the equilibrium concentrations of all species.
  2. At 25oC, KP = 5.3x105 for the reaction N2(g) + 3H2(g) ↔ 2NH3(aq). When a certain partial pressure of NH3(g) is put into an otherwise empty rigid vessel at 25oC, equilibrium is reached when 50.0% of the original ammonia has decomposed. What was the original partial pressure of ammonia before any decomposition occurred?
  3. The partial pressures of an equilibrium mixture of N2O4(g) and NO2(g) are PN2O4 = 0.34atm an PNO2 = 1.20atm at a certain temperature. The volume of the container is doubled. Find the partial pressures of the two gases when a new equilibrium is established.
  4. An 8.00g sample of SO3 was placed in an evacuated container, where it decomposes at 600oC according to the following reaction: SO3(g) ↔ SO2(g) + 1/2O2(g). At equilibrium the total pressure and the density of the gaseous mixture were 1.80atm and 1.60g/L, respectively. Calculate KP for this reaction.

Answer Key.

  1. See answers in classroom WS Packet binder.25. [H2] = [F2] = 0.0251M, and [HF] = 0.450M
  2. (a) 0.11(b) 77(c) 8.8(d) 1.7x10-426. See answers in classroom WS Packet binder.
  3. 6.9x10-4
  4. 1.7x10-5
  5. 6.3x10-13
  6. 1.5x108
  7. 8.0x109
  8. (a) QK, left(b) Q=K, same(c) QK, right
  9. (a) decrease(b) no change(c) no change(d) decrease
  10. 0.096M
  11. 3.4
  12. 0.056
  13. [SO3] = [NO] = 1.06M and [SO2] = [NO2] = 0.54M
  14. 7.8x10-2atm
  15. PSO2 = 0.38atm, PO2 = 0.44atm and PSO3 = 0.12atm
  16. (a) [NO] = 0.032M, [Cl2] = 0.016M, and [NOCl] = 1.0M (b) [NO] = [NOCl] = 1.0M, [Cl2] = 1.6x10-5

(c) [NO] = 8.0x10-3M, [Cl2] = 1.0M, and [NOCl] = 2.0M

  1. [CO2] = 0.39M, [CO] = 8.6x10-3M, [O2] = 4.3x10-3M
  2. 0.27atm
  3. See answers in classroom WS Packet binder.
  4. See answers in classroom WS Packet binder.
  5. See answers in classroom WS Packet binder.
  6. 2.6x1081
  7. [N2]0 = 10.0M; [H2]0 = 11.0
  8. (a) 1.16atm(b) 0.10atm(c) 2.22atm(d) 91.4%

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